Creating own editor type
See API docs - Preface:


  The Blender/Python API can’t (yet)...
  
  
  Create new space types.
  


It can only be done in the C code:
http://wiki.blender.org/index.php/Dev:2.6/Source/Tutorials/AddAnEditor

Nonetheless,


you may use draw handlers to overlay an existing editor with python-drawn content. Check out OpenGL Wrapper (bgl) and Font Drawing (blf).
or build blender with the Py-Buttons patch by Campbell Barton to create python-drawn widgets:
http://www.youtube.com/watch?v=mRiTfLpRlRU
(seems to crash if applied to current trunk, use an older revision or wait for a fix)